I don't know much about the regulation of 501(c)7 organizations, but I do note that they can receive up to 15% of their gross revenues from non-member use of facilities and/or services. You can find more information at the IRS website, http://www.irs.gov/charities/nonprofits/article/0,,id=96189,.... You may want to look at the last link on the page which will take you to the IRM audit guide for 501(c)7 organizations. This will detail what an IRS agent would be looking at should the instigate an audit of your Guild.